I glued on a piece to hold the mdf together and put together my dust extractor.

I'm building a cocktail cabinet at the moment which is takin up all my time. I will hopefully Cnc the parts, which needs some careful planning. I now have autocad installed and have started sketching it out.

Will turn the teardrop soon.

Also have purchased some MA ch70's.

And hopefully ordering a carton of Alpair 10.2 for kittin out a bar I am re-modelling.

High-pass filtering a drive unit does not change its power rating per se. The A7.3 is rated to 20w; adding a filter doesn't change that, but you will improve the overall system power-handling ability / dynamic range since it has to do less work in the < 500Hz region. For e.g., in a sealed box, Qtc 0.7, at the 20w rated input, you'll never get anywhere near the rated Xmax; just over 1mm is about the lot. Sans filter, at 100Hz in the same box for the same power input, displacement will be about 3x that (this is assuming you've dealt with the LF impedance peak). In other words, with the filter in place, you should be able to achieve the ~98.9dB (1m) theoretical maximum the driver is capable of at the rated input without running out of mechanical travel, which would normally prevent this being practically achieved.

The nominal power-handling is still 20w. However, by high-passing the driver it no longer has to handle the low frequencies where the greatest power demands are, significantly reducing excursion. The limits therefore become thermal / electrical rather than mechanical. Sans filters, at 20w input you're rapidly running out of travel; with the filter in place, this is much reduced. See the attached deflection plots for the 7.3 at 1m/20w -yellow is QB3 vented box, blue Qtc .707 sealed box, purple Qtc .707 sealed box with 1st order high-pass at 400Hz.

Note that the 20w figure is a nominal; the A7 can handle somewhat more, but this isn't a free reign to come it the neanderthal; it's a large tweeter, not a 15in pro-audio woofer.

No. The nominal rated power input of the Mark Audio Alpair 7 is 20w. It can take a bit more than that in practice (probably ~30-35w for brief [repeat: BRIEF] bursts), but 20w is the nominal rated input. That doesn't change whether you high pass it, low pass it, bandpass it, or are on the northern polar cap of Mars dancing the tango with Rachel Weisz.

By high passing the drive unit at 400Hz, you are reducing the amount of power applied to it in the low frequency region, where most of the power demands in a musical signal are to be found. This results in lower excursion levels, since the driver is not being asked to handle these low frequencies, so you will not likely get near its mechanical limits. However, you still need to pay attention to the electrical / thermal limits since if you apply too much power beyond what it is rated at, you could burn out the voice coil.